So, I purchased a new house this winter and it's time to turn on the sprinklers...hopefully the previous owners blew them out last fall. So, I found the main valve and upon turning it on water spews out of the anti-siphon valve that sticks out of the ground about 5 feet away. I've never had an anti-siphon valve on my systems in the past so I have no idea what they really do. Is there something that I should be doing to prevent this or is it broke?